How many more hundreds to make a thousand from 400?

There are 20 children in the cast of a class play and 8 of the children are boys of the boys 4 have a speaking part in the play and of the girls 8 do not have a speaking part in the play if a child from the cast of the place chosen at random what is the probability that the child has a speaking part

Ineed to know the answer to this algebra question.

Which of the following is not a subset of {1,2,3}?